Object manoeuvring apparatus

ABSTRACT

An apparatus ( 12 ) for manoeuvring a downhole object ( 22 ) comprises a casing ( 28 ) and a carriage ( 34 ) slidably mounted within the casing ( 28 ), wherein the carriage ( 34 ) defines a cylinder bore ( 62 ) extending at least partially into a side wall thereof. An engaging member ( 64 ) comprising a piston body ( 66 ) is slidably mounted within the cylinder bore ( 62 ) of the carriage ( 34 ) and is arranged to divide the bore ( 62 ) into first and second piston chambers ( 68, 70 ). The engaging member ( 64 ) is arranged to extend through the wall portion of the carriage ( 34 ) between extended and retracted positions to selectively engage an object ( 22 ) to be manoeuvred. In one disclosed embodiment, the apparatus ( 12 ) is for use in displacing a tool ( 22 ) for setting or retrieving a plug ( 26 ) in or from a Christmas tree ( 132 ).

FIELD OF THE INVENTION

The present invention relates to an apparatus for manoeuvring a downhole object, and in particular, but not exclusively, to an apparatus for manoeuvring a tool to set a plug in or retrieve a plug from a Christmas tree.

The present invention also relates to a subsea tool deployment system which incorporates an apparatus for manoeuvring a downhole object.

BACKGROUND TO THE INVENTION

Subsea oil and gas production wells are sealed off from the environment using apparatus known as production Christmas trees. Two types of tree are commonly used, namely a vertical tree and a horizontal tree. The vertical tree has gate valves in the production bore allowing isolation of the well through the remote operation of these valves. The horizontal tree, also known as a spool Christmas tree, relies on plugs to seal the production bore, wherein the plugs are run into a tubing hanger installed inside the tree.

Increasingly, horizontal type trees are being used with subsea wells for reasons of cost and convenience. Horizontal trees allow wells to be brought into production in less time and at lower cost than vertical Christmas trees. Furthermore, horizontal trees allow for more modern and larger bore completion systems to be used in the well.

However, significant problems have been encountered when trying to correctly set plugs in the tree, or when trying to recover plugs from the tree. For example, the plug can be set in similar, but incorrect profiles within the tree resulting in low integrity sealing of the well. Additionally, large forces are required to set or retrieve the plug from the tree. Furthermore, there is often no positive indication that the plug has been correctly set. Since the plugs are primary barriers in isolating the high pressure hydrocarbon well fluids from the environment, it is critical they are correctly placed and fitted within the Christmas tree system. Additionally, it is also essential that the plugs are capable of being removed when required.

Increasingly, the oil and gas industry is seeking to perform many well associated operations from a subsea location, thus eliminating the costs, difficulties and hazards of tying all operations back to a surface vessel, such as a floating platform or the like. The difficulties associated with tying back to a surface vessel, for example via a marine riser, are well known and documented in the art.

Of particular interest are recent developments in subsea systems which are used to deploy tools into a well, such as intervention tools. The present applicant has proposed a self-contained subsea intervention system which is capable of being mounted on an existing Christmas tree to deploy tools to perform various intervention operations within the well. More specifically, the applicant's system, such as is described in WO 2004/065757, includes a chamber within which a number of intervention tools are stored. The required tools are selected from the chamber and subsequently run into the well bore through the Christmas tree. Once the operation is completed the tools are retrieved and again stored. As the intervention system is mounted on the Christmas tree, it is necessary for the appropriate fluid barriers associated with Christmas trees, such as plugs, to be set in place or activated prior to landing and securing the intervention system on the tree. Once the system is secured in place the fluid barriers must be removed or deactivated. Furthermore, the barriers must again be set in place before decoupling the system from the tree.

Accordingly, there is a requirement in the art for subsea systems to incorporate an appropriate apparatus for removing and setting in place fluid barriers, such as well bore plugs. Additionally, as many subsea systems are required to be self-contained, it is very important that the appropriate apparatus is extremely robust and efficient, with minimal risk of failure.

WO 2005/103442, owned by the present applicant, describes a plug setting and retrieving apparatus which incorporates an axially moveable member which carriers a plurality of radially moveable members. In use, the radially moveable members are moved radially inwardly to engage a plug pulling tool, and the axially moveable member is then moved in the appropriate direction to move the tool to either set a plug within or retrieve a plug from a Christmas tree. However, control of the stroking motion of the radially member is limited.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided an apparatus for manoeuvring a downhole object, said apparatus comprising:

a casing;

a carriage slidably mounted within the casing, wherein the carriage defines a cylinder bore extending at least partially into a side wall thereof; and

an engaging, member comprising a piston body slidably mounted within the cylinder bore of the carriage and arranged to divide the bore into first and second piston chambers, wherein the engaging member is adapted to extend through the wall portion of the carriage between extended and retracted positions to selectively engage an object to be manoeuvred.

It should be understood that “downhole object” as used herein relates to any object which may be located or is intended to be located within a subterranean bore, such as a wellbore, and also to any object which is located within equipment or apparatus which is coupled to or mounted on a subterranean bore, such as a wellhead apparatus or the like.

In use, the engaging member may be moved to an extended position to engage an object located adjacent the carriage to thus secure the object relative to the carriage, and the carriage may then be moved within the casing to move or translate the object in the desired manner or direction.

The carriage may be moveable along at least one line of movement. In one embodiment the carriage may be moveable in an axial direction relative to the casing of the apparatus.

The engaging member may be laterally moveable relative to the carriage. In one embodiment the engaging member may be radially moveable relative to the carriage and the casing. The engaging member may be adapted to be translated radially inwardly relative to the carriage. Alternatively, or additionally, the engaging member may be adapted to be translated radially outwardly.

In one embodiment of the present invention, a plurality of engaging members may be provided and received within respective cylinder bores within the carriage. The engaging members may be evenly distributed around the carriage.

The engaging member may comprise a boss extending from one side of the piston body and adapted to engage an object to be manoeuvred. The carriage may define a throughbore extending through the side wall thereof and merging with the cylinder bore, wherein the throughbore is adapted to receive the boss. In a preferred embodiment, the throughbore describes a smaller diameter than the cylinder bore.

The boss may be circular in cross-section.

Two or more bosses may be provided, and may be axially spaced apart relative to the longitudinal axis of the casing.

The boss may be integrally formed with the piston body. Alternatively, the boss may be separately formed and subsequently secured to the piston body.

The piston body may be circular in cross-section. Alternatively, the piston body may be non-round in cross-section, for example generally oval or elongated, i.e., is longer in one direction relative to a transverse direction. In this arrangement the piston body is preferably mounted within the carriage such that the longitudinal extent of the piston body is aligned with the longitudinal axis of the carriage. This arrangement permits a greater stroking distance of the piston body to be achieved. However, the surface area of a non-round piston body may have a smaller surface area than that of a round piston body and as such may be exert a lower force when exposed to equivalent fluid pressure.

The carriage may be adapted to be actuated hydraulically, pneumatically, mechanically or the like, or by any suitable combination thereof. In a preferred embodiment, the carriage defines a piston and is adapted to be hydraulically actuated within the casing.

The piston body may be adapted to be actuated to move or reconfigure the engaging member between said extended and retracted positions. The piston body may be adapted to be actuated hydraulically, pneumatically, mechanically or the like, or by any suitable combination thereof.

In one embodiment, the piston body may be adapted to be actuated hydraulically. The piston body may define a double acting piston body and the first and second piston chambers defined on either side of the piston body may be in fluid communication with a source of hydraulic power. Accordingly, in this arrangement the engaging member is capable of being positively actuated in reverse directions thus providing increased control over the operation of the apparatus of the present invention.

The casing may define at least one fluid port extending through a wall portion thereof for communicating fluid to and from the first and second piston chambers. The at least one fluid port may communicate directly with the first and second piston chambers, or alternatively may communicate indirectly, for example via a cavity or the like formed within the casing.

A first fluid port may extend through a wall portion of the casing for delivering hydraulic fluid to the first piston chamber. The first fluid port may communicate directly with the first piston chamber. Alternatively, the first fluid port may communicate indirectly with the first piston chamber, for example via a cavity defined within the casing. Where a plurality of engaging members are provided, the first fluid port may be adapted to deliver fluid to more than one of said plurality of engaging members. For example, in one arrangement the first fluid port may communicate with a cavity in fluid communication with each of the first piston chambers. Alternatively, each first piston chamber may receive fluid through individual fluid ports.

A second fluid port may extend through a wall portion of the casing for delivering fluid to the second piston chamber. The second fluid port may communicate directly with the second piston chamber. Alternatively, the second fluid port may communicate indirectly with the second piston chamber, for example via a cavity defined within the casing. Where a plurality of engaging members are provided, the second fluid port may be adapted to deliver fluid to more than one of said plurality of engaging members. For example, in one arrangement the second fluid port may communicate with a cavity in fluid communication with each of the second piston chambers. Alternatively, each second piston chamber may receive fluid through individual hydraulic ports.

The carriage may be generally tubular in shape and define an axial throughbore adapted to receive an object to be manoeuvred by the apparatus. Accordingly, in this arrangement, in use, an object may be positioned within the through bore of the carriage, the engaging member may be actuated via the piston body to move radially inwardly to engage the object, and the carriage may subsequently be axially translated to displace the object in the desired direction.

The carriage may be annular and may define an annular carriage sleeve, wherein a wall of the annular sleeve extends generally axially. A proportion of the wall of the carriage may be generally aligned parallel with a central axis of the carriage.

The carriage may have a uniform wall thickness. Alternatively, the carriage may comprise at least two regions having different wall thickness. In this arrangement the carriage may be defined generally by at least two coaxial cylinders joined together or integrally formed in end-to-end relation. The regions may be arranged such that at least one or both of the outer and inner wall surfaces of the carriage is non-uniform. It should be understood that by non-uniform it is meant that the diameter described by the respective surfaces is not uniform across the axial extent of the carriage. The engaging member is disposed in at least one of the regions, preferably within the region with the greater wall thickness.

A transition region may be defined between adjacent regions of the carriage providing a transition in wall thicknesses between said adjacent regions. The transition region may be provided on at least one and preferably both of the inner and outer wall surfaces of the carriage. A portion of the transition region may be tapered and may define a generally frusto-conical region. Alternatively, or additionally, at least a portion of the transition region may be stepped and define an annular surface facing in a generally axial direction. The annular surface may define a limiting surface adapted to limit movement of the carriage within the casing. In this embodiment the casing may define a corresponding surface region adapted to be selectively engaged with the annular surface of the carriage.

In one embodiment the carriage may comprise three regions axially arranged to define first and second axially opposed end regions and a central region disposed between the first and second end regions. In some embodiments, the central region may have a smaller wall thickness than at least one of the end regions. However, in a currently preferred embodiment the central region defines a greater wall thickness than the end regions. In this embodiment the end regions may have different wall thicknesses, or alternatively, and in a preferred embodiment, have equivalent wall thicknesses.

Advantageously, a respective transition region may be defined between the central region and each of the end regions. In a preferred embodiment, the transition regions comprise a stepped surface extending generally radially outwardly from a respective outer surface of both the first and second end regions. The stepped surfaces may define first and second annular surfaces. In this embodiment the casing may define corresponding first and second annular surfaces adapted to be engaged with the first and second annular surfaces of the carriage. Accordingly, the first and second annular surfaces of the housing may delineate a working stroke of the carriage such that movement of the carriage is limited between said first and second annular surfaces.

The engaging member may be mounted within the central region of the carriage.

The casing may define an annular recess, wherein at least a portion of the central region of the carriage may be adapted to be received and translated within said annular recess. The annular recess may circumferentially surround the central region and has an axial length greater than that of said central region such that said central region may stroke within the annular recess. Advantageously, the annular recess is defined by an inner wall surface of the casing and the first and second annular surfaces thereof, as defined above, such that movement of the carriage is restricted within the annular recess between said first and second annular surfaces.

First and second annular chambers may be defined between the carriage and the annular recess, wherein the volume of the respective annular chambers varies in accordance with movement of the carriage. That is, movement of the carriage to reduce the volume of the first annular chamber may result in a corresponding increase in the volume of the second chamber, and vice versa.

The first and second annular chambers may be in fluid communication with each other to permit fluid to pass therebetween, for example upon movement of the carriage. This arrangement therefore prevents or substantially minimises hydraulic locking of the carriage from occurring. In one embodiment a fluid port extends through the central region of the carriage between the first and second annular chambers.

In one embodiment of the present invention, one of the first and second piston chambers defined on either side of the piston body may be in fluid communication with at least one of the first and second annular chambers, for example via a fluid port. At least one and preferably both of the first and second annular chambers may be adapted to receive fluid, for example via a fluid port extending through the wall of the casing. Accordingly, fluid may be communicated to and from at least one of the first and second piston chambers via at least one of the annular chambers.

A fluid cavity may be defined between an outer surface of the central region of the carriage and an inner wall of the annular recess of the casing, wherein one of the first and second piston chambers defined on either side of the piston body may be in fluid communication with the fluid cavity. The piston chamber may open directly into the fluid cavity such that direct fluid communication is achieved. Alternatively, a fluid port may be provided between the piston chamber and fluid cavity.

The fluid cavity may be sealed at either end by sealing members, such as o-rings extending around the circumference of the outer surface of the central region of the carriage. The sealing members may therefore prevent or minimise the leakage of fluid between the chamber and the annular chambers. The sealing members are advantageously adapted to define a sliding seal, such that sealing is achieved when the carriage is moved within the casing.

The casing may define first and second annular piston chambers adapted to receive the first and second end regions, respectively, of the carriage, wherein the first and second annular piston chambers are adapted to receive a fluid for actuating the carriage to stroke within the casing. The first and second annular pistons may be adapted to receive a fluid via respective fluid ports extending through the wall of the casing and communication with each chamber.

The first and second annular piston chambers may be integrally formed with the casing. Alternatively, at least one sleeve member may be mounted within the casing to define, at least partially, the first and second annular piston chambers.

In one embodiment of the present invention, the apparatus further comprises a carriage sensor adapted to sense the position of the carriage relative to the casing. The carriage sensor may be adapted to sense the axial position of the carriage relative to the casing.

The carriage sensor may be a non-contact sensor, for example an inductance sensor or magnetic sensor. For example, a magnet or array of magnets may be disposed on one of the carriage and the casing, and a magnetic sensor or array of sensors may be disposed on the other of the carriage and casing, such that passage of a magnet passed a sensor will be detected.

In an alternative embodiment the carriage sensor may be a contact sensor. In one embodiment the sensor may be mounted on one of the carriage and casing and comprise a displacement member adapted to physically engage a contact surface on the other of the carriage and casing. In use, the sensor is adapted to determine the displacement of the displacement member caused by contact with the contact surface. Displacement of the displacement member may be established inductively.

In one embodiment the displacement member comprises a plunger. Also, in a preferred embodiment the sensor is mounted on the casing and displacement member extends through a wall of the casing and engages a contact surface provided on the carriage. The contact surface may comprise a ramped surface, such that axial movement of the carriage will cause displacement of the displacement member by engaging with the ramped surface.

The apparatus may further comprise an engaging member sensor adapted to sense the position of the engaging member. In one embodiment the engaging member sensor may be a contact sensor. The sensor may be mounted, on the casing and comprise a displacement member adapted to physically engage a contact surface on the engaging member. In use, the sensor is adapted to determine the displacement of the displacement member caused by contact with the contact surface. Displacement of the displacement member may be established inductively.

In one embodiment the displacement member comprises a plunger. Also, in a preferred embodiment the sensor is mounted on the casing and the displacement member extends through a wall of the casing and engages a contact surface provided on the engaging member. The contact surface may comprise a rear side face of the piston body of the engaging member.

In one embodiment the apparatus of the present invention is adapted for use in manoeuvring a downhole tool, and specifically adapted for manoeuvring a downhole tool for retrieving plugs from and setting plugs in a wellhead assembly, such as a Christmas tree. In this arrangement, a plug pulling tool may be positioned within the apparatus and subsequently gripped with the engaging member, following which the carriage may be actuated to move the plug pulling tool in the required direction.

Advantageously, the apparatus of the present invention may be adapted to be mounted on an external assembly. The casing may define a flange portion adapted to be secured to a corresponding flange portion of the external assembly. The apparatus may further comprise a sealing adaptor to be engaged with the flange portion of the external assembly, wherein the sealing adaptor comprises a sealing member adapted to provide a seal between the sealing adaptor and the flange of the external assembly. The sealing adaptor advantageously eliminates the requirement to provide a sealing member on the flange portion of the casing, thus permitting the overall diameter of the casing to be minimised. Additionally, the presence of the sealing adaptor permits the apparatus of the present invention to be utilised on conventional external assemblies.

The apparatus may be adapted for subsea use.

Additionally, the apparatus of the present invention may be adapted to be mounted on external assemblies such as Christmas trees, wellheads, well control packages and the like.

The apparatus of the present invention may be adapted to provide support for further apparatus or assemblies, such as tool storage chambers, winch assemblies, or the like. An upper portion of the casing may define a conventional Christmas tree connector such that, in situations where the apparatus is secured to a Christmas tree, other apparatus, such as conventional workover risers and the like may be secured relative to the Christmas tree without first removing the apparatus of the present invention.

In one embodiment the apparatus of the present invention is adapted for use in a tool deployment system.

According to a second aspect of the present invention, there is provided a tool deployment system comprising:

an apparatus according to the first aspect mounted on a wellhead; and

a tool storage package mounted relative to the apparatus, wherein the tool storage package comprises a chamber for storing a tool.

The apparatus may be mounted on a wellhead via a Christmas tree, such as a horizontal Christmas tree. The apparatus according to the first aspect may be adapted for use in removing plugs from and setting plugs within the Christmas tree.

The tool deployment system may further comprise a winch assembly comprising a spoolable medium, such as wireline, adapted to be coupled to a downhole tool and deploy and retrieve the tool into and from a wellbore.

According to a third aspect of the present invention, there is provided a method of manoeuvring a downhole object, said method comprising the steps of:

providing an apparatus according to the first aspect and mounting said apparatus relative to a subterranean bore;

positioning an object adjacent to the carriage;

actuating the engaging member to move to engage the object;

actuating the carriage to move the object; and

actuating the engaging member to move to release the object.

In one embodiment the object is a tool for use in releasing or setting in place a plug within a Christmas tree, wherein the apparatus is adapted to move the tool and thus the plug.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a subsea assembly incorporating an apparatus, for manoeuvring an object according to an embodiment of an aspect of the present invention;

FIG. 2 is a longitudinal cross-sectional view of the subsea assembly of FIG. 1;

FIG. 3 is an enlarged cross-sectional view of the apparatus of the present invention;

FIG. 4 is an enlarged cross-sectional view of a portion of the apparatus of the present invention;

FIG. 5 is a perspective view of components of the apparatus according to one embodiment of the present invention;

FIG. 6 is a perspective view of components of the apparatus according to an alternative embodiment of the present invention; and

FIG. 7 is a diagrammatic representation of the apparatus of the present invention shown installed within a tool deployment system in accordance with an embodiment of an aspect of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is first made to FIG. 1 in which there is shown a subsea assembly in the form of a well control package, generally identified by reference numeral 10, wherein the package 10 incorporates an apparatus, specifically a plug pulling apparatus 12, according to an embodiment of an aspect of the present invention. As will be described in further detail below, the plug pulling apparatus 12 in the embodiment shown is for use in retrieving and setting plugs within a Christmas tree (not shown).

The well control package 10 forms part of a tool deployment system and includes a valve assembly 14 mounted on a Christmas tree connector 16 via a flanged connection 18, such that the valve assembly 14 may be secured to a Christmas tree (not shown) via said connector 16. The plug pulling assembly 12 is mounted on the valve assembly 14 via a flanged connection 20. It should be understood that the plug pulling assembly 12 of the present invention is not limited for use in the manner shown and may be used in combination with any other equipment.

Reference is now made to FIG. 2 of the drawings in which there is shown a cross-sectional view of the well control package 10 of FIG. 1. The cross-section in FIG. 2 is viewed in the direction of arrow A of FIG. 1.

As mentioned above, the well control package 10 in the embodiment shown forms part of a subsea tool deployment system which, in use, is mounted on a Christmas tree (not shown). When the tool deployment system is required for use, for example to perform well intervention operations within a well, production will be stopped and appropriate plugs will be set in the Christmas tree to isolate the Christmas tree and wellbore from the environment. Following this, the tool deployment system will be landed on top of the tree and connected thereto via the tree connector 16. However, in order to provide access to the well bore the tree plugs must again be removed, which is achieved by the plug pulling assembly 12.

Specifically, an elongate plug pulling tool 22, which is diagrammatically represented in phantom outline, is run through the plug pulling assembly 12 and valve assembly 14, for example on wireline 24, and engages the appropriate tree plug 26, also diagrammatically shown in phantom outline. Once the tree plug 26 is sufficiently engaged, the plug pulling apparatus 12 is reconfigured, as described in detail hereinafter, to grip the elongate plug pulling tool 22. Following this, the apparatus moves the tool 22 in an upward direction to retrieve the plug 26 from the tree. The tool 22 and plug may then be moved to a storage position within the tool deployment system.

When the tool deployment system is no longer required, the tree plug 26 must again be set in the tree prior to removing the tool deployment system. To achieve this the tool 22 is again run through the apparatus 12 and valve assembly 14, is gripped by the apparatus 12 and then forced in a downward direction to set the plug 26 in place. The apparatus may then once again apply an upward force on the tool 22 to test the integrity of the plug 26. Following this the tool 22 may be disengaged from the plug 26 and returned to a storage position, after which the entire tool deployment system including the well control package 10 may be decoupled from the tree.

The structure and operation of the plug pulling apparatus 12 will now be described in detail with reference initially to FIG. 3, which is a cross-sectional view of one side of the apparatus 12. The apparatus 12 comprises a casing 28 which includes an axial throughbore 29 and which includes a lower flange 30 to be coupled to the valve assembly 14 (FIG. 1) and an upper connector 32 to be coupled to the remaining portions of the tool deployment system. The upper connector 32 in the embodiment shown is identical to the connector on the Christmas tree upon which the apparatus 12 is mounted. Accordingly, conventional equipment which may be required to be coupled to the tree may be coupled thereto without requiring the apparatus 12 to first be removed.

A carriage 34 in the form of a sleeve is mounted within the casing 28 and is adapted to slide axially relative thereto. The carriage 34 is formed of three regions, specifically a cylindrical central region 36 and first and second cylindrical end regions 38, 40 disposed on either side of the central region 36. In the embodiment shown the central region 36 has a greater wall thickness than that of the end regions 38, 40, and the end regions 38, 40 have substantially equal wall thicknesses.

The first and second end regions 38, 40 are disposed in first and second annular chambers 42, 44 respectively. The first annular chamber 42 is defined between an outer surface of an upper sleeve 46 fitted within the bore 29 of the casing 28, and the inner surface of the casing 28. The second annular chamber 44 is defined between facing surfaces of outer and inner lower sleeves 48, 50 fitted within the bore 29 of the casing 28. It should be noted that the outer sleeve 48 is provided separately from the casing 28 to permit insertion of the carriage 36 through the flange portion 30 during assembly of the apparatus 12.

A fluid port 52 extends through the wall of the casing 28 and provides fluid communication of hydraulic fluid into the first chamber 42. Additionally, a fluid port 54 extends through the wall of the casing 28 and provides fluid communication of hydraulic fluid into the second chamber 44. Accordingly, hydraulic fluid may be communicated to and from the chambers 42, 44 through the respective ports 52, 54 to cause the carriage 34 to be displaced axially relative to the casing 28.

The central region 36 of the carriage 34 is disposed within an annular recess 56 formed within the casing 28, wherein annular recess 56 limits the stroke of the carriage 34. An upper annular chamber 58 is formed between an upper end of the central region 36 of the carriage 34 and an upper region of the annular recess 56. A lower annular chamber 60 is formed between a lower end region of the central region 36 and a lower region of the annular recess 56. The relative volumes of the upper and lower chambers 58, 60 vary during stroking of the carriage 34. It should be noted that the carriage 34 is shown in a fully upward stroked configuration such that the volume of the upper chamber 58 is at a minimum and the volume of the lower chamber 60 is at a maximum.

Referring briefly to FIG. 4, a plurality of axial bores 61 (only one shown in FIG. 4) extend through the central region 36 of the carriage 34 to thus provide fluid communication between the upper and lower annular chambers 58, 68. This fluid communication assists to prevent hydraulic locking of the carriage 34 during stroking within the casing 28.

Reference is again made to FIG. 3. The central region 36 of the carriage 34 defines three cylinder bores 62 (only one shown) which partially extend through the wall of the central region 36 from an external surface thereof. The cylinder bores 62 are evenly circumferentially distributed around the central region 36 of the carriage 34.

An engaging member 64 including a piston body 66 is slidably mounted within each cylinder bore 62 of the carriage 36, wherein the piston body 66 divides the bore 42 into a first piston chamber 68 defined by the piston body 64 and side and bottom walls of the bore 62, and a second piston chamber 70 defined by the piston body 64, side walls of the cylinder bore 62 and the inner surface of the casing 28. The engaging member 64 further comprises a pair of axially spaced bosses 72, 74 extending from the piston body 66, through the second piston chamber 70 and through respective bores 76, 78 within the carriage 34 and thus into the bore 29 of the casing 28. In use, the engaging member 64 is caused to stroke radially to extend the bosses into the bore 29 to engage the plug pulling tool 22 (FIG. 2), and to retract the bosses 72, 74 from the bore 29 to disengage the plug pulling tool 22. The engaging member 64 is shown in a fully retracted position such that the volume of the first piston chamber 68 is at a maximum and the volume of the second piston chamber 70 is at a minimum.

Accordingly, in use, the plug pulling tool 22 (FIG. 2) may be positioned within the bore 29 of the casing 28 and the engaging members 64 extended to engage the bosses 72, 74 with the outer circumference of the tool 22. In this respect the tool 22 may define a profile which is engaged with a corresponding profile on the bosses 72, 74 to ensure sufficient engagement. Once the tool 22 is secured by the engaging members 64, the carriage 34 may be stroked in the required direction to displace the tool 22.

A fluid port 80 extends through the wall of the casing 28 and communicates with a cavity defined between the inner surface of the annular recess 56 and an outer surface of the central region 36 of the carriage 34. Upper and lower seals in the form of o-rings 82, 84 seal the cavity from the upper and lower annular chambers 58, 60. Each cylinder bore 62 opens into the cavity such that the second piston chamber 70 of each cylinder bore 62 is in fluid communication with said cavity. Accordingly, fluid communicated through the fluid port 80 will enter the second piston chamber 70 of each cylinder bore to cause the engaging member 64 to stroke radially inwards. Additionally, when the engaging member 64 is caused to stroke radially outwards, as will be discussed below, fluid within the second piston chamber 70 may be displaced or vented through the port 80.

The first piston chamber 68 of each cylinder bore 62 is in fluid communication with the annular recess 56, and specifically with the lower annular chamber 60 via respective fluid ports 81. A further fluid port 83 extends through the wall of the casing 29 and communicates with the lower annular chamber 60 of the annular recess 56. Accordingly, in use, fluid may be communicated through the port 83 into the annular recess 56 and subsequently into the first piston chamber 68 via fluid port 81 to cause the engaging member 34 to stroke radially outwards. Additionally, when the engaging member 34 is caused to stroke radially inwards, fluid within the first piston chamber 68 may be displaced or vented through port 81 and into the annular recess 56, and subsequently through port 83. Accordingly, the engaging member 34 may be positively controlled to stroke in reverse directions providing full control over the operation of the apparatus 12.

It should be understood that each port 52, 54, 80 and 83 are shown within the same plane. However, this arrangement is for convenience of the present description and it should be understood that the ports 52, 54, 80 and 83 may be distributed around the circumference of the casing.

As noted above, the carriage 34 is installed within the casing 28 through the bottom end thereof, together with the lower outer and inner sleeves 48, 50. In order to accommodate insertion of these components while achieving a bore 29 which is of uniform diameter, the lower end of the casing includes an access bore 85 of a large diameter which encroaches into the flange 30. As such, the sealing area 86 of the flange portion 30 is greatly reduced which prevents its use with conventional subsea compact flange connectors. In order to ensure that a sufficient flange seal can be accommodated, the plug pulling apparatus 12 of the present invention incorporates a sealing ring 88 positioned within the access bore 85 to extend the effective sealing surface area 86 of the flange 30. The sealing ring 88 includes a circular groove 90 which in use accommodates a sealing member for providing a seal when the casing 28 is secured to the valve assembly 14 (FIG. 1), or other subsea assembly.

It should be noted that the sealing ring 88 may be used in other apparatus and is not limited for use with the apparatus 12 of the present invention.

A sensor arrangement for use within the apparatus 12 of the present invention will now be described with reference to FIG. 4 in which an enlarged cross sectional view of the central region 36 of the carriage 34 is shown. The sensor arrangement includes two sensors 92 (only one shown in FIG. 4) for sensing the position of the carriage 34 relative to the casing 29. Also, the sensor arrangement includes three sensors 94 (only one shown in FIG. 4) for sensing the position of a respective engaging member 64 relative to the carriage 34. The sensors 92, 94 are circumferentially distributed around the casing 29 as shown in FIG. 1.

The form and function of the sensor 92 will first be described. The sensor 92 includes a housing 96 which is secured to the casing 28 via bolts (not shown in FIG. 4). A sensing element 98 in the form of an inductance sensor extends through and is threadably secured within a bore 100 in the rear end of the housing 96, and extends into a counter bore 102. A plunger 104 having a blind bore 106 is mounted over the sensing element 98 and within the counter bore 102 to extend therefrom and through a bore 107 formed through the wall of the casing 28. A coil spring 108 is positioned between the plunger 104 and a base wall of the counter bore 102 and acts to bias the plunger 104 towards an extended position. The sensor 92 is arranged such that the position of the plunger 104 relative to the sensing element 98 is determined, for example, by a measured inductance from said sensing element 98. The relative position of the plunger 104 may then be used to determine the position of the carriage 34, as discussed in more detail below.

A ramp surface 110 is formed on an outer surface of the central region 36 of the carriage 34 at the locations of the sensors 92, wherein the ramp surface 110 is arranged to be engaged by a tip 112 of the plunger 104. In use, when the carriage 34 strokes in a downward direction, the ramp surface 110 will permit the plunger 104 to be further extended relative to the sensing element 98 by action of the spring 108. When the carriage 34 strokes in an upward direction, the ramp surface 110 will cause the plunger to be depressed against the bias of the spring 108. A geometric function may be used to establish the stroke position of the carriage 34 based on the relative position of the plunger 104 and sensing element 98.

Referring still to FIG. 4, the function of the sensor 94 will now be described. It should be noted that the sensor 94 is identical to the sensor 92 described above and as such comprises a housing 114, inductance sensing element 116, plunger 118 and coil spring 120 acting to bias the plunger 118 towards an extended position. A tip 122 of the plunger 114 engages a rear surface on the engaging member 64. It should be noted that the sensor 94 is located generally centrally relative to the annular recess 56 formed within the casing 29 such that the plunger 118 may engage the engaging member 34 at all times during stroking of the carriage 34. In use, when the engaging member 64 strokes radially inwardly the plunger 118 will be extended relative to the sensing element 116 by action of the spring 120, and when the engaging member 64 strokes radially outwardly the plunger will be depressed against the bias of the spring 120. A measured inductance of the sensing element 116 may therefore be used to determine the relative position of the plunger 118 and sensing element 116, and thus the position of the engaging member 64.

Although sensors 92 and 94 are defined above as inductance sensors, it should be understood that any suitable displacement sensor, particularly linear displacement sensors, may be utilised.

Reference is now made to FIGS. 5 and 6 of the drawings in which there is shown perspective views of the carriage 34 which incorporates alternative forms of engaging member 64. The engaging member 64 a shown in FIG. 5 includes a generally round piston body 66 a, whereas the engaging member 64 b shown in FIG. 6 includes a generally elongate piston body 66 b. The elongate piston body 66 b is mounted within the cylinder bore 62 such that the longitudinal direction of the piston body 66 b is aligned with the longitudinal direction of the carriage 34. Accordingly, the extent of the piton body 66 b which extends in a lateral direction relative to the carriage 34 is less than that of the piston body 66 a shown in FIG. 5. This arrangement therefore permits the piston body 66 b to stroke a greater distance within the cylinder bore 62 than the round piston body 66 a. As such, the elongate arrangement of engaging member 64 b may be preferred in circumstances where a large stroking distance is required.

However, it should be noted that the round piston body 66 a presents a greater surface area than the elongate piston body 66 b and as such will be capable of applying a greater force on a tool 22 (FIG. 2) for the same fluid actuation pressure.

Reference is now made to FIG. 7 in which there is shown a diagrammatic representation of the apparatus 12 of the present invention installed within a tool deployment system, generally identified by reference numeral 130, in accordance with an embodiment of an aspect of the present invention.

The tool deployment system 130 is mounted on a Christmas tree 132 which in turn is mounted on a wellhead 134 of a well bore 136. As described above, a well control package 10 is mounted on the Christmas tree 132. Specifically, the well control package includes the valve assembly 14 which is mounted on the Christmas tree 132 via the tree connector 16, and the plug pulling apparatus 12 of the present invention is mounted above the valve assembly 14. A tool storage package 138 is mounted above the plug pulling apparatus 12 and includes a tool storage chamber 140 which contains a plurality of downhole tools 142. The tool storage chamber is in fluid communication with the well bore 136 via the well control package 10, Christmas tree 132 and well head 136 such that the stored tools 142 are exposed to bore fluids.

A winch assembly 144 is mounted above the tool storage assembly 138 and comprises a winch chamber 146 within which is located a vertically mounted winch drum 148 which carries a spool of wireline 150. In use, the wireline 150 extends upwardly from the winch chamber 146 through a first lubricator tube 152, over a sheave 154 and down through a second lubricator tube 156. The winch chamber 146 is in fluid communication with the tool storage chamber 140 via the lubricator tubes 152, 156 and sheave 154. The wireline 150 then extends through a central axis of the winch drum 148 and into the tool chamber 140. In use, a tool 142 is selected from the tool chamber 140 and secured to the end of the wireline 150 and subsequently run into the wellbore 136.

When the tool deployment system 130 is required for use, production from the wellbore 136 is ceased and an appropriate tree plug 26 is set in place to isolate the wellbore 36. The tool deployment system 130 may then be landed on and secured to the Christmas tree 132. In order to remove the plug 26 to provide access to the wellbore 36 a plug pulling tool 22 is selected from the tool chamber 140, secured to the wireline 150 and run through the plug pulling assembly 12 and valve assembly 14 to engage the plug 26. The plug pulling assembly 12 may then be activated in the manner described above to grip the tool 22 and pull the plug 26 from the Christmas tree 132. The tool 22 and plug 26 may then be pulled upwards by the wireline 150 and stored within the tool storage chamber 140. The necessary tools 142 may then be selected and run into the wellbore 136 to perform the required in well operations, such as intervention operations.

Once the tool deployment system 130 is no longer required, the plug 26 may again be set in place within the Christmas tree 132 and the tool deployment system 130 removed.

It should be understood that the embodiments described above are merely exemplary and that various modifications may be made thereto without departing from the scope of the invention. For example, the plug pulling apparatus is not restricted for use above a valve assembly, nor for use exclusively within a tool deployment system. 

1. An apparatus for manoeuvring a downhole object, said apparatus comprising: a casing; a carriage slidably mounted within the casing, wherein the carriage defines a cylinder bore extending at least partially into a side wall thereof; and an engaging member comprising a piston body slidably mounted within the cylinder bore of the carriage and arranged to divide the bore into first and second piston chambers, wherein the engaging member is adapted to extend through the wall portion of the carriage between extended and retracted positions to selectively engage an object to be manoeuvred.
 2. The apparatus according to claim 1, wherein, in use, the engaging member is moved to an extended position to engage an object located adjacent the carriage to thus secure the object relative to the carriage, and the carriage then be moved within the casing to move or translate the object in the desired manner or direction.
 3. The apparatus according to claim 1, wherein the carriage is moveable in an axial direction relative to the casing of the apparatus.
 4. The apparatus according to claim 1, wherein the engaging member is radially moveable relative to the carriage and the casing.
 5. The apparatus according to claim 1, wherein a plurality of engaging members are provided and received within respective cylinder bores within the carriage.
 6. The apparatus according to claim 1, wherein the engaging member comprises a boss extending from one side of the piston body and adapted to engage an object to be manoeuvred.
 7. The apparatus according to claim 6, wherein the carriage defines a throughbore extending through the side wall thereof and merging with the cylinder bore, wherein the throughbore is adapted to receive the boss.
 8. The apparatus according to claim 1, wherein the carriage defines a piston and is adapted to be hydraulically actuated within the casing.
 9. The apparatus according to claim 1, wherein the piston body is adapted to be actuated to move or reconfigure the engaging member between said extended and retracted positions.
 10. The apparatus according to claim 1, wherein the piston body defines a double acting piston body and the first and second piston chambers defined on either side of the piston body are in fluid communication with a source of fluid power.
 11. The apparatus according to claim 1, wherein the casing defines at least one fluid port extending through a wall portion thereof for communicating fluid to and from the first and second piston chambers.
 12. The apparatus according to claim 11, wherein the at least one fluid port communicates directly with the first and second piston.
 13. The apparatus according to claim 11, wherein the at least one fluid port communicates indirectly with the first and second piston, via a cavity.
 14. The apparatus according to claim 1, wherein the carriage is generally tubular in shape and defines an axial throughbore adapted to receive an object to be manoeuvred by the apparatus.
 15. The apparatus according to claim 1, wherein the carriage comprises at least two regions having different wall thickness.
 16. The apparatus according to claim 15, wherein the engaging member is disposed a region with the greater wall thickness.
 17. The apparatus according to claim 15, wherein a transition region is defined between adjacent regions of the carriage providing a transition in wall thicknesses between said adjacent regions.
 18. The apparatus according to claim 17, wherein the transition region defines a limiting surface adapted to limit movement of the carriage within the casing.
 19. The apparatus according to claim 1, wherein the carriage comprises three regions axially arranged to define first and second axially opposed end regions and a central region disposed between the first and second end regions.
 20. The apparatus according to claim 19, wherein the central region defines a greater wall thickness than the end regions.
 21. The apparatus according to claim 19, wherein a respective transition region is defined between the central region and each of the end regions.
 22. The apparatus according to claim 19, wherein the engaging member is mounted within the central region of the carriage.
 23. The apparatus according to claim 19, wherein the casing defines an annular recess, and at least a portion of the central region of the carriage is received and translated within said annular recess.
 24. The apparatus according to claim 23, wherein first and second annular chambers are defined between the carriage and the annular recess, wherein the volume of the respective annular chambers varies in accordance with movement of the carriage.
 25. The apparatus according to claim 24, wherein the first and second annular chambers are in fluid communication with each other to permit fluid to pass therebetween.
 26. The apparatus according to claim 24, wherein one of the first and second piston chambers defined on either side of the piston body is in fluid communication with at least one of the first and second annular chambers.
 27. The apparatus according to claim 19, wherein the casing defines first and second annular piston chambers adapted to receive the first and second end regions, respectively, of the carriage, wherein the first and second annular piston chambers are adapted to receive a fluid for actuating the carriage to stroke within the casing.
 28. The apparatus according to claim 1, further comprising a carriage sensor adapted to sense the position of the carriage relative to the casing.
 29. The apparatus according to claim 28, wherein the carriage sensor is mounted on one of the carriage and casing and comprises a displacement member adapted to physically engage a contact surface on the other of the carriage and casing, wherein the sensor is adapted to determine the displacement of the displacement member caused by contact with the contact surface.
 30. The apparatus according to claim 29, wherein the contact surface comprises a ramped surface, such that axial movement of the carriage will cause displacement of the displacement member by engaging with the ramped surface.
 31. The apparatus according to claim 1, further comprising an engaging member sensor adapted to sense the position of the engaging member.
 32. The apparatus according to claim 31, wherein the engaging member sensor is mounted on the casing and comprise a displacement member adapted to physically engage a contact surface on the engaging member.
 33. The apparatus according to claim 1, adapted for use in manoeuvring a downhole tool for retrieving plugs from and setting plugs in a wellhead assembly.
 34. The apparatus according to claim 1, wherein the casing defines a flange portion adapted to be secured to a corresponding flange portion of an external assembly.
 35. The apparatus according to claim 34, further comprising a sealing adaptor to be engaged with the flange portion of the external assembly, wherein the sealing adaptor comprises a sealing member adapted to provide a seal between the sealing adaptor and the flange of the external assembly.
 36. The apparatus according to claim 1, adapted for subsea use.
 37. A tool deployment system comprising: an apparatus mounted on a wellhead; and a tool storage package mounted relative to the apparatus, wherein the tool storage package comprises a chamber for storing a tool, wherein the apparatus comprises: a casing; a carriage slidably mounted within the casing, wherein the carriage defines a cylinder bore extending at least partially into a side wall thereof; and an engaging member comprising a piston body slidably mounted within the cylinder bore of the carriage and arranged to divide the bore into first and second piston chambers, wherein the engaging member is adapted to extend through the wall portion of the carriage between extended and retracted positions to selectively engage an object to be manoeuvred.
 38. A method of manoeuvring a downhole object, said method comprising the steps of: mounting an apparatus relative to a subterranean bore, wherein the apparatus comprises: a casing; a carriage slidably mounted within the casing, wherein the carriage defines a cylinder bore extending at least partially into a side wall thereof; and an engaging member comprising a piston body slidably mounted within the cylinder bore of the carriage and arranged to divide the bore into first and second piston chambers, wherein the engaging member is adapted to extend through the wall portion of the carriage between extended and retracted positions to selectively engage an object to be manoeuvred; positioning an object adjacent to the carriage; actuating the engaging member to move to engage the object; actuating the carriage to move the object; and actuating the engaging member to move to release the object. 